EE 706: ComputerCommunication Networks
Networking Technologies
IIT-Bombay
Manjunath: Computer Communicatin Networks – p.1
Networking
� Information technology is as much aboutmanipulating information as about moving ortransporting information.
Networking deals with Information Transport.More specifically, the mechanisms that governthe sharing of the resources in the bit carrierinfrastructure.
Manjunath: Computer Communicatin Networks – p.2
Networking
� Information technology is as much aboutmanipulating information as about moving ortransporting information.
� Networking deals with Information Transport.More specifically, the mechanisms that governthe sharing of the resources in the bit carrierinfrastructure.
Manjunath: Computer Communicatin Networks – p.2
Technology: Discussion Outline
� Identify functional elements ofnetworking—Multiplexing, Switching, Routingand Management.
Current practice in networking where we describethe Bit Carrier Infrastructure and the seven layerISO-OSI model for networking.
Finally, an overview of the three dominantnetworking technologies—Telephone Network,Internet and Asynchronous Transfer ModeNetworks.
Quick overview of ‘other’ networks like X.25 andFrame Relay.
Manjunath: Computer Communicatin Networks – p.3
Technology: Discussion Outline
� Identify functional elements ofnetworking—Multiplexing, Switching, Routingand Management.
� Current practice in networking where we describethe Bit Carrier Infrastructure and the seven layerISO-OSI model for networking.
Finally, an overview of the three dominantnetworking technologies—Telephone Network,Internet and Asynchronous Transfer ModeNetworks.
Quick overview of ‘other’ networks like X.25 andFrame Relay.
Manjunath: Computer Communicatin Networks – p.3
Technology: Discussion Outline
� Identify functional elements ofnetworking—Multiplexing, Switching, Routingand Management.
� Current practice in networking where we describethe Bit Carrier Infrastructure and the seven layerISO-OSI model for networking.
� Finally, an overview of the three dominantnetworking technologies—Telephone Network,Internet and Asynchronous Transfer ModeNetworks.
Quick overview of ‘other’ networks like X.25 andFrame Relay.
Manjunath: Computer Communicatin Networks – p.3
Technology: Discussion Outline
� Identify functional elements ofnetworking—Multiplexing, Switching, Routingand Management.
� Current practice in networking where we describethe Bit Carrier Infrastructure and the seven layerISO-OSI model for networking.
� Finally, an overview of the three dominantnetworking technologies—Telephone Network,Internet and Asynchronous Transfer ModeNetworks.
� Quick overview of ‘other’ networks like X.25 andFrame Relay.
Manjunath: Computer Communicatin Networks – p.3
Preliminaries
� Points at which networked information servicesconnect to generators and absorbers ofinformation flow, called sources and sinksrespectively
Example sources: telephone transmitters, videocameras, file on a disk, etc
Example sinks: telephone receivers, videomonitors, storage devices,
source/sink
source/sink
source/sink
source/sink
source/sink
source/sink
distributedinformation applications
Manjunath: Computer Communicatin Networks – p.4
Preliminaries
� Points at which networked information servicesconnect to generators and absorbers ofinformation flow, called sources and sinksrespectively
� Example sources: telephone transmitters, videocameras, file on a disk, etc
Example sinks: telephone receivers, videomonitors, storage devices,
source/sink
source/sink
source/sink
source/sink
source/sink
source/sink
distributedinformation applications
Manjunath: Computer Communicatin Networks – p.4
Preliminaries
� Points at which networked information servicesconnect to generators and absorbers ofinformation flow, called sources and sinksrespectively
� Example sources: telephone transmitters, videocameras, file on a disk, etc
� Example sinks: telephone receivers, videomonitors, storage devices, � � �
source/sink
source/sink
source/sink
source/sink
source/sink
source/sink
distributedinformation applications
Manjunath: Computer Communicatin Networks – p.4
Preliminaries
� Points at which networked information servicesconnect to generators and absorbers ofinformation flow, called sources and sinksrespectively
� Example sources: telephone transmitters, videocameras, file on a disk, etc
� Example sinks: telephone receivers, videomonitors, storage devices, � � �
source/sink
source/sink
source/sink
source/sink
source/sink
source/sink
distributedinformation applications
Manjunath: Computer Communicatin Networks – p.4
A Layered View
Bit Carrier Infrastructure
Resource Sharing Mechanisms
sources and/or sinksnetworked applications
Common Information Services
Multiplexing, scheduling, routing,network management
Information Services
Communication Links
infrastructure and traffic flow:
buffering, jitter removal, etc.browsers, source compression, storage,User interfaces, transducers, servers,
Dynamic and intelligent control of
"NETWORKING"
WDM, Optical Crossconnects, SDH, DSL,"cable", Ethernet, satellite, fixed or mobilewireless links
A three-layered view of a communication network.“Networking” is concerned with resource sharingmechanisms that efficiently share the bit carrierinfrastructure, and control the quality of serviceprovided to the various applications using the network
Manjunath: Computer Communicatin Networks – p.5
A Layered View
� A layered view helps in identifying anddistinguishing different classes of functions.
Similar to the concept of subroutines or functionsin programming.
Three layersInformation Services LayerBit Carrier Infrastructure Layer“Networking” Layer
Manjunath: Computer Communicatin Networks – p.6
A Layered View
� A layered view helps in identifying anddistinguishing different classes of functions.
� Similar to the concept of subroutines or functionsin programming.
Three layersInformation Services LayerBit Carrier Infrastructure Layer“Networking” Layer
Manjunath: Computer Communicatin Networks – p.6
A Layered View
� A layered view helps in identifying anddistinguishing different classes of functions.
� Similar to the concept of subroutines or functionsin programming.
� Three layers
Information Services LayerBit Carrier Infrastructure Layer“Networking” Layer
Manjunath: Computer Communicatin Networks – p.6
A Layered View
� A layered view helps in identifying anddistinguishing different classes of functions.
� Similar to the concept of subroutines or functionsin programming.
� Three layers
� Information Services Layer
Bit Carrier Infrastructure Layer“Networking” Layer
Manjunath: Computer Communicatin Networks – p.6
A Layered View
� A layered view helps in identifying anddistinguishing different classes of functions.
� Similar to the concept of subroutines or functionsin programming.
� Three layers
� Information Services Layer
� Bit Carrier Infrastructure Layer
“Networking” Layer
Manjunath: Computer Communicatin Networks – p.6
A Layered View
� A layered view helps in identifying anddistinguishing different classes of functions.
� Similar to the concept of subroutines or functionsin programming.
� Three layers
� Information Services Layer
� Bit Carrier Infrastructure Layer
� “Networking” Layer
Manjunath: Computer Communicatin Networks – p.6
Information Services LayerH/W and S/W to facilitate the transport serviceand attach the source and sink.
� Encode information from source into atransportable form and decode receivedinformation into usable form.
ExamplesVoice coding, packet buffering and playout,and voice decoding for packet telephony;Mail preparation and forwarding software forelectronic mail;Browser for the WWW.
Manjunath: Computer Communicatin Networks – p.7
Information Services LayerH/W and S/W to facilitate the transport serviceand attach the source and sink.
� Encode information from source into atransportable form and decode receivedinformation into usable form.
� Examples
Voice coding, packet buffering and playout,and voice decoding for packet telephony;Mail preparation and forwarding software forelectronic mail;Browser for the WWW.
Manjunath: Computer Communicatin Networks – p.7
Information Services LayerH/W and S/W to facilitate the transport serviceand attach the source and sink.
� Encode information from source into atransportable form and decode receivedinformation into usable form.
� Examples
� Voice coding, packet buffering and playout,and voice decoding for packet telephony;
Mail preparation and forwarding software forelectronic mail;Browser for the WWW.
Manjunath: Computer Communicatin Networks – p.7
Information Services LayerH/W and S/W to facilitate the transport serviceand attach the source and sink.
� Encode information from source into atransportable form and decode receivedinformation into usable form.
� Examples
� Voice coding, packet buffering and playout,and voice decoding for packet telephony;
� Mail preparation and forwarding software forelectronic mail;
Browser for the WWW.
Manjunath: Computer Communicatin Networks – p.7
Information Services Layer
� Handle network induced imperfections—loss,delay, delay variations
Define the allowable imperfections from thenetwork—Quality of Service (QoS) as statistical(mean, percentiles) or deterministic (bounds)guarantees
Example QoS measures: service denial(blocking), delay, delay variations, loss,reordering, etc.
Manjunath: Computer Communicatin Networks – p.8
Information Services Layer
� Handle network induced imperfections—loss,delay, delay variations
� Define the allowable imperfections from thenetwork—Quality of Service (QoS) as statistical(mean, percentiles) or deterministic (bounds)guarantees
Example QoS measures: service denial(blocking), delay, delay variations, loss,reordering, etc.
Manjunath: Computer Communicatin Networks – p.8
Information Services Layer
� Handle network induced imperfections—loss,delay, delay variations
� Define the allowable imperfections from thenetwork—Quality of Service (QoS) as statistical(mean, percentiles) or deterministic (bounds)guarantees
� Example QoS measures: service denial(blocking), delay, delay variations, loss,reordering, etc.
Manjunath: Computer Communicatin Networks – p.8
Bit Carrier InfrastructureThe raw material for building the informationtransport superstructure.
� The issues here are those from a classicalcommunication course—modulation, capacity,channel coding, medium characteristics, etc.
Reasonable to assume that the channel is digital.
We assume that the communication links areimperfect bit pipes in the sense that these pipescan delay, lose or modify the bits that they carry.
Manjunath: Computer Communicatin Networks – p.9
Bit Carrier InfrastructureThe raw material for building the informationtransport superstructure.
� The issues here are those from a classicalcommunication course—modulation, capacity,channel coding, medium characteristics, etc.
� Reasonable to assume that the channel is digital.
We assume that the communication links areimperfect bit pipes in the sense that these pipescan delay, lose or modify the bits that they carry.
Manjunath: Computer Communicatin Networks – p.9
Bit Carrier InfrastructureThe raw material for building the informationtransport superstructure.
� The issues here are those from a classicalcommunication course—modulation, capacity,channel coding, medium characteristics, etc.
� Reasonable to assume that the channel is digital.
� We assume that the communication links areimperfect bit pipes in the sense that these pipescan delay, lose or modify the bits that they carry.
Manjunath: Computer Communicatin Networks – p.9
NetworkingUses the raw material of communication links andprovides the networking services that the informationservices assumes.
� The link design problem is concerned with the bitflow—extract the maximum bit rate possible,Networking is concerned with information flow.
Manjunath: Computer Communicatin Networks – p.10
Computer System Analogy
DistributedInformation Applications
DistributedAlgorithms for
Information Transport(e.g., X.25, Internet, ATM)
Applications
ComputerOperating System
(e.g., Unix, Linux, Windows)
disk drives, sound card)
analogy with the operating systemof a computer
Communication Links
Network of
Hardware
(e.g.,calculation, accounting, database)
(e.g., processor, memory,
(e.g., www, e−commerce, teleconf)
Networking is concerned with distributed algorithmsfor efficient sharing of bit carrier network resources.Very similar to OS of a computer helping applicationsto use and share hardware resources.
Manjunath: Computer Communicatin Networks – p.11
Functional Elements
� Consider a sample information flow.
After source prepares the bits for transportation,“network” decides how to route flow overphysical network.
Infrastructure is shared by many such flows.Hence network has to decide how to multiplexedthis flow with other flows.
Flow may traverse multiple links. At junction oftwo links, switch flow elements to target link.
Need to monitor network behaviour and collectstatus information; possibly handle situations forwhich network is not engineered. i.e., performnetwork management.
Manjunath: Computer Communicatin Networks – p.12
Functional Elements
� Consider a sample information flow.
� After source prepares the bits for transportation,“network” decides how to route flow overphysical network.
Infrastructure is shared by many such flows.Hence network has to decide how to multiplexedthis flow with other flows.
Flow may traverse multiple links. At junction oftwo links, switch flow elements to target link.
Need to monitor network behaviour and collectstatus information; possibly handle situations forwhich network is not engineered. i.e., performnetwork management.
Manjunath: Computer Communicatin Networks – p.12
Functional Elements
� Consider a sample information flow.
� After source prepares the bits for transportation,“network” decides how to route flow overphysical network.
� Infrastructure is shared by many such flows.Hence network has to decide how to multiplexedthis flow with other flows.
Flow may traverse multiple links. At junction oftwo links, switch flow elements to target link.
Need to monitor network behaviour and collectstatus information; possibly handle situations forwhich network is not engineered. i.e., performnetwork management.
Manjunath: Computer Communicatin Networks – p.12
Functional Elements
� Consider a sample information flow.
� After source prepares the bits for transportation,“network” decides how to route flow overphysical network.
� Infrastructure is shared by many such flows.Hence network has to decide how to multiplexedthis flow with other flows.
� Flow may traverse multiple links. At junction oftwo links, switch flow elements to target link.
Need to monitor network behaviour and collectstatus information; possibly handle situations forwhich network is not engineered. i.e., performnetwork management.
Manjunath: Computer Communicatin Networks – p.12
Functional Elements
� Consider a sample information flow.
� After source prepares the bits for transportation,“network” decides how to route flow overphysical network.
� Infrastructure is shared by many such flows.Hence network has to decide how to multiplexedthis flow with other flows.
� Flow may traverse multiple links. At junction oftwo links, switch flow elements to target link.
� Need to monitor network behaviour and collectstatus information; possibly handle situations forwhich network is not engineered. i.e., performnetwork management.
Manjunath: Computer Communicatin Networks – p.12
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
Two types of multiplexing:Circuit multiplexing.Packet multiplexing.
Manjunath: Computer Communicatin Networks – p.13
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
� Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
Two types of multiplexing:Circuit multiplexing.Packet multiplexing.
Manjunath: Computer Communicatin Networks – p.13
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
� Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
� Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
Two types of multiplexing:Circuit multiplexing.Packet multiplexing.
Manjunath: Computer Communicatin Networks – p.13
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
� Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
� Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
� Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
Two types of multiplexing:Circuit multiplexing.Packet multiplexing.
Manjunath: Computer Communicatin Networks – p.13
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
� Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
� Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
� Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
� Two types of multiplexing:
Circuit multiplexing.Packet multiplexing.
Manjunath: Computer Communicatin Networks – p.13
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
� Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
� Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
� Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
� Two types of multiplexing:
� Circuit multiplexing.
Packet multiplexing.
Manjunath: Computer Communicatin Networks – p.13
Multiplexing
� Communications links or bit pipes are expensiveresources and possibly imperfect.
� Need to amortise cost among a large number ofsources—need mechanism to share efficiently.
� Assume information flow requirements—sourceand destination and capacity required, is a time avarying process.
� Sharing the communication link ismultiplexing—technique used for systematicallymerging several data flows into one bit-pipe.
� Two types of multiplexing:
� Circuit multiplexing.
� Packet multiplexing.Manjunath: Computer Communicatin Networks – p.13
Circuit Multiplexing on a Link
� Link capacity is statically partitioned intochannels (possibly differentcapacities)—Frequency, Time, Space and CodeDivision Multiplexing.
Standards specify partitioning details, e.g.,CCITT and North American standards for TDM.
Each conversation (flow) is allocated to a channelfor the entire duration of call—the call holds thechannel.
Connection setup is required to allocateresources.
Fixed rate allocated at time of connection setupdetermines the peak rate at which the source cantransmit data.
Manjunath: Computer Communicatin Networks – p.14
Circuit Multiplexing on a Link
� Link capacity is statically partitioned intochannels (possibly differentcapacities)—Frequency, Time, Space and CodeDivision Multiplexing.
� Standards specify partitioning details, e.g.,CCITT and North American standards for TDM.
Each conversation (flow) is allocated to a channelfor the entire duration of call—the call holds thechannel.
Connection setup is required to allocateresources.
Fixed rate allocated at time of connection setupdetermines the peak rate at which the source cantransmit data.
Manjunath: Computer Communicatin Networks – p.14
Circuit Multiplexing on a Link
� Link capacity is statically partitioned intochannels (possibly differentcapacities)—Frequency, Time, Space and CodeDivision Multiplexing.
� Standards specify partitioning details, e.g.,CCITT and North American standards for TDM.
� Each conversation (flow) is allocated to a channelfor the entire duration of call—the call holds thechannel.
Connection setup is required to allocateresources.
Fixed rate allocated at time of connection setupdetermines the peak rate at which the source cantransmit data.
Manjunath: Computer Communicatin Networks – p.14
Circuit Multiplexing on a Link
� Link capacity is statically partitioned intochannels (possibly differentcapacities)—Frequency, Time, Space and CodeDivision Multiplexing.
� Standards specify partitioning details, e.g.,CCITT and North American standards for TDM.
� Each conversation (flow) is allocated to a channelfor the entire duration of call—the call holds thechannel.
� Connection setup is required to allocateresources.
Fixed rate allocated at time of connection setupdetermines the peak rate at which the source cantransmit data.
Manjunath: Computer Communicatin Networks – p.14
Circuit Multiplexing on a Link
� Link capacity is statically partitioned intochannels (possibly differentcapacities)—Frequency, Time, Space and CodeDivision Multiplexing.
� Standards specify partitioning details, e.g.,CCITT and North American standards for TDM.
� Each conversation (flow) is allocated to a channelfor the entire duration of call—the call holds thechannel.
� Connection setup is required to allocateresources.
� Fixed rate allocated at time of connection setupdetermines the peak rate at which the source cantransmit data. Manjunath: Computer Communicatin Networks – p.14
Circuit Multiplexing on a Link(contd)
� A call (request for resources) can be blocked if allthe channels are busy.
Performance measures: Connection setup delayand call blocking probability.
A typical design problem: What should be thelink capacity for a given load and specifiedblocking probability.
The link may also have to handle different classesof flows each with a different blockingprobability requirement.
Manjunath: Computer Communicatin Networks – p.15
Circuit Multiplexing on a Link(contd)
� A call (request for resources) can be blocked if allthe channels are busy.
� Performance measures: Connection setup delayand call blocking probability.
A typical design problem: What should be thelink capacity for a given load and specifiedblocking probability.
The link may also have to handle different classesof flows each with a different blockingprobability requirement.
Manjunath: Computer Communicatin Networks – p.15
Circuit Multiplexing on a Link(contd)
� A call (request for resources) can be blocked if allthe channels are busy.
� Performance measures: Connection setup delayand call blocking probability.
� A typical design problem: What should be thelink capacity for a given load and specifiedblocking probability.
The link may also have to handle different classesof flows each with a different blockingprobability requirement.
Manjunath: Computer Communicatin Networks – p.15
Circuit Multiplexing on a Link(contd)
� A call (request for resources) can be blocked if allthe channels are busy.
� Performance measures: Connection setup delayand call blocking probability.
� A typical design problem: What should be thelink capacity for a given load and specifiedblocking probability.
� The link may also have to handle different classesof flows each with a different blockingprobability requirement.
Manjunath: Computer Communicatin Networks – p.15
Circuit multiplexing: ResourceAllocation Model
time
link c
apacity
channelslink
Static partitioning of bandwidth in a circuit switchednetwork
Manjunath: Computer Communicatin Networks – p.16
Circuit Multiplexing Ineffi-ciency
� Most sources generate data in bursts:
Voice: Talk and silence spurtsVideo: Scene changesTelnet: Typing behaviourWeb browsing patterns: Think times betweendownloads
Manjunath: Computer Communicatin Networks – p.17
Circuit Multiplexing Ineffi-ciency
� Most sources generate data in bursts:
� Voice: Talk and silence spurts
Video: Scene changesTelnet: Typing behaviourWeb browsing patterns: Think times betweendownloads
Manjunath: Computer Communicatin Networks – p.17
Circuit Multiplexing Ineffi-ciency
� Most sources generate data in bursts:
� Voice: Talk and silence spurts
� Video: Scene changes
Telnet: Typing behaviourWeb browsing patterns: Think times betweendownloads
Manjunath: Computer Communicatin Networks – p.17
Circuit Multiplexing Ineffi-ciency
� Most sources generate data in bursts:
� Voice: Talk and silence spurts
� Video: Scene changes
� Telnet: Typing behaviour
Web browsing patterns: Think times betweendownloads
Manjunath: Computer Communicatin Networks – p.17
Circuit Multiplexing Ineffi-ciency
� Most sources generate data in bursts:
� Voice: Talk and silence spurts
� Video: Scene changes
� Telnet: Typing behaviour
� Web browsing patterns: Think times betweendownloads
Manjunath: Computer Communicatin Networks – p.17
Motivating Packet Multiplexing
data emitted by a computer
PCM voice with activity detection
variable bit rate video
video frames (e.g., 30 frames/sec)
talk spurt silence
random epochs of data emission
bit rate
bits
in e
ach
fram
ebi
ts in
eac
h em
issi
on
scenechange
Traffic flow from sources is typically bursty
� Average rate is much lower than peak rate.
Capacity is wasted during “lean periods”.
Manjunath: Computer Communicatin Networks – p.18
Motivating Packet Multiplexing
data emitted by a computer
PCM voice with activity detection
variable bit rate video
video frames (e.g., 30 frames/sec)
talk spurt silence
random epochs of data emission
bit rate
bits
in e
ach
fram
ebi
ts in
eac
h em
issi
on
scenechange
Traffic flow from sources is typically bursty
� Average rate is much lower than peak rate.
� Capacity is wasted during “lean periods”.Manjunath: Computer Communicatin Networks – p.18
Packet Multiplexingtime
link ca
pacity
link
packets from various connections
Packet Multiplexing: No partitioning of the bit pipe
� Packets will need to contain header and trailerinformation to identify with a specificinformation flow (source, destination,application, etc.).
Apply entire bit rate to a source and hence, eachpacket gets the entire bit pipe for shorter periodsof time.
Manjunath: Computer Communicatin Networks – p.19
Packet Multiplexingtime
link ca
pacity
link
packets from various connections
Packet Multiplexing: No partitioning of the bit pipe
� Packets will need to contain header and trailerinformation to identify with a specificinformation flow (source, destination,application, etc.).
� Apply entire bit rate to a source and hence, eachpacket gets the entire bit pipe for shorter periodsof time.
Manjunath: Computer Communicatin Networks – p.19
Packet Multiplexing
� Source peak rate can exceed link rate—packetsmay need to be queued. If buffer capacity is notsufficient, packets may be dropped and hencelost.
Abstraction: Link is a server serving customerswaiting in a queue.
Performance measures: Packet delay and losscharacteristics.
Manjunath: Computer Communicatin Networks – p.20
Packet Multiplexing
� Source peak rate can exceed link rate—packetsmay need to be queued. If buffer capacity is notsufficient, packets may be dropped and hencelost.
� Abstraction: Link is a server serving customerswaiting in a queue.
Performance measures: Packet delay and losscharacteristics.
Manjunath: Computer Communicatin Networks – p.20
Packet Multiplexing
� Source peak rate can exceed link rate—packetsmay need to be queued. If buffer capacity is notsufficient, packets may be dropped and hencelost.
� Abstraction: Link is a server serving customerswaiting in a queue.
� Performance measures: Packet delay and losscharacteristics.
Manjunath: Computer Communicatin Networks – p.20
Centralised Packet MultiplexingTERMINAL
TERMINAL
TERMINAL
TERMINAL
HOST
HOST
MUX MUX
multiplexer ports
full-duplex link
Centralised packet multiplexing: multiplexers havefull control over link’s transmission rate.
� Multiplexer stuffs packets on to link; hascomplete control over link.
Scheduler can decide sequence of transmissions.
Manjunath: Computer Communicatin Networks – p.21
Centralised Packet MultiplexingTERMINAL
TERMINAL
TERMINAL
TERMINAL
HOST
HOST
MUX MUX
multiplexer ports
full-duplex link
Centralised packet multiplexing: multiplexers havefull control over link’s transmission rate.
� Multiplexer stuffs packets on to link; hascomplete control over link.
� Scheduler can decide sequence of transmissions.Manjunath: Computer Communicatin Networks – p.21
Distributed Packet Multiplexing
link
NODES
Distributed packet multiplexing: sources share link ina distributed fashion.
� Sources (hosts/nodes) connected to a multipointlink (wiretap, wireless channel).
Manjunath: Computer Communicatin Networks – p.22
Distributed Packet Multiplexing
� Only one source can successfully transmit on thechannel at any time—multiple access channel.
Design Issue: Coordination among the sources.Random access: collision recognition andresolution.Controlled access: various flavours ofpolling—central or distributed.Reservation access: Usually for satellitechannels.
Manjunath: Computer Communicatin Networks – p.23
Distributed Packet Multiplexing
� Only one source can successfully transmit on thechannel at any time—multiple access channel.
� Design Issue: Coordination among the sources.
Random access: collision recognition andresolution.Controlled access: various flavours ofpolling—central or distributed.Reservation access: Usually for satellitechannels.
Manjunath: Computer Communicatin Networks – p.23
Distributed Packet Multiplexing
� Only one source can successfully transmit on thechannel at any time—multiple access channel.
� Design Issue: Coordination among the sources.
� Random access: collision recognition andresolution.
Controlled access: various flavours ofpolling—central or distributed.Reservation access: Usually for satellitechannels.
Manjunath: Computer Communicatin Networks – p.23
Distributed Packet Multiplexing
� Only one source can successfully transmit on thechannel at any time—multiple access channel.
� Design Issue: Coordination among the sources.
� Random access: collision recognition andresolution.
� Controlled access: various flavours ofpolling—central or distributed.
Reservation access: Usually for satellitechannels.
Manjunath: Computer Communicatin Networks – p.23
Polling Based MultiplexingToken ring
node
node
node
node
Manjunath: Computer Communicatin Networks – p.24
Reservation Based MultiplexingA Satellite System Example (VSAT Network)
VSAT
VSAT
router
routercampusnetwork
campusnetwork
packetswitch
DIU
DIU
� Inbound channel to the hub is shared.
Propagation delay is large, no instantaneousfeedback of result of the transmission—cannotuse polling or contention based random access.
Manjunath: Computer Communicatin Networks – p.25
Reservation Based MultiplexingA Satellite System Example (VSAT Network)
VSAT
VSAT
router
routercampusnetwork
campusnetwork
packetswitch
DIU
DIU
� Inbound channel to the hub is shared.
� Propagation delay is large, no instantaneousfeedback of result of the transmission—cannotuse polling or contention based random access.
Manjunath: Computer Communicatin Networks – p.25
VSAT System
� Ask for reservations from the hub using somecontention mechanism
Successful reservations and the frame structuresare communicated on the outbound channel to theusers
Manjunath: Computer Communicatin Networks – p.26
VSAT System
� Ask for reservations from the hub using somecontention mechanism
� Successful reservations and the frame structuresare communicated on the outbound channel to theusers
Manjunath: Computer Communicatin Networks – p.26
Multiplexing Summary
multiplexing
circuit multiplexed packet multiplexed
centralised distributed
random access
polledaccess
reservationaccess
token passingmaster−slave
Manjunath: Computer Communicatin Networks – p.27
Hybrid solutions
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� � � � � � � � � � � � � � � � � � � � � � � � �
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� � � � � � � � � � � � � � � � � � � � � � � � �circuitmultiplexed
packetmultiplexed
movableboundary
Hybrid link multiplexing; combining circuitmultiplexing and packet multiplexing on a link.
� Partition capacity into circuit & packetmultiplexing parts.
Important example: “2B+D” ISDN services
More complex solutions vary boundary; rarelyimplemented.
Manjunath: Computer Communicatin Networks – p.28
Hybrid solutions
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
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� � � � � � � � � � � � � � � � � � � � � � � � �
circuitmultiplexed
packetmultiplexed
movableboundary
Hybrid link multiplexing; combining circuitmultiplexing and packet multiplexing on a link.
� Partition capacity into circuit & packetmultiplexing parts.
� Important example: “2B+D” ISDN services
More complex solutions vary boundary; rarelyimplemented.
Manjunath: Computer Communicatin Networks – p.28
Hybrid solutions
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
� � � � � � � � � � � � � � � � � � � � � � � � �
circuitmultiplexed
packetmultiplexed
movableboundary
Hybrid link multiplexing; combining circuitmultiplexing and packet multiplexing on a link.
� Partition capacity into circuit & packetmultiplexing parts.
� Important example: “2B+D” ISDN services
� More complex solutions vary boundary; rarelyimplemented.
Manjunath: Computer Communicatin Networks – p.28
Switching: Motivation
S2S1
S
(c)
(b)(a)
A six node network constructed in three ways—(a) Abrute force way. (b) Every node is connected to acentral switch
�that selectively establishes paths
between nodes and (c) Hierarchical network withinter-switch links with possibly multiplexing on it.
Manjunath: Computer Communicatin Networks – p.29
Switching
switchlink link
link
� Information flow will traverse more than one link.
Switch is required at junction of two or morelinks.
Switch is a device that selectively establishes andreleases connections between communicationlinks to allow sharing of these links among anumber of flows (connections).
Manjunath: Computer Communicatin Networks – p.30
Switching
switchlink link
link
� Information flow will traverse more than one link.
� Switch is required at junction of two or morelinks.
Switch is a device that selectively establishes andreleases connections between communicationlinks to allow sharing of these links among anumber of flows (connections).
Manjunath: Computer Communicatin Networks – p.30
Switching
switchlink link
link
� Information flow will traverse more than one link.
� Switch is required at junction of two or morelinks.
� Switch is a device that selectively establishes andreleases connections between communicationlinks to allow sharing of these links among anumber of flows (connections).
Manjunath: Computer Communicatin Networks – p.30
Switching (contd)
� Switch moves information from link to link bydemultiplexing on the inbound link andmultiplexing on the selected outbound link.
A switch is required with circuit multiplexing andcentralised packet multiplexing.
Manjunath: Computer Communicatin Networks – p.31
Switching (contd)
� Switch moves information from link to link bydemultiplexing on the inbound link andmultiplexing on the selected outbound link.
� A switch is required with circuit multiplexing andcentralised packet multiplexing.
Manjunath: Computer Communicatin Networks – p.31
Functions of a Switch
� Two categories, also called planes offunctions—data plane and control plane
Data plane functionsDemultiplex the flow (e.g., packet or timeslot) on the input link.Switch the flow element onto the appropriateoutput link.Multiplex the flows on the output link.
Manjunath: Computer Communicatin Networks – p.32
Functions of a Switch
� Two categories, also called planes offunctions—data plane and control plane
� Data plane functions
Demultiplex the flow (e.g., packet or timeslot) on the input link.Switch the flow element onto the appropriateoutput link.Multiplex the flows on the output link.
Manjunath: Computer Communicatin Networks – p.32
Functions of a Switch
� Two categories, also called planes offunctions—data plane and control plane
� Data plane functions
� Demultiplex the flow (e.g., packet or timeslot) on the input link.
Switch the flow element onto the appropriateoutput link.Multiplex the flows on the output link.
Manjunath: Computer Communicatin Networks – p.32
Functions of a Switch
� Two categories, also called planes offunctions—data plane and control plane
� Data plane functions
� Demultiplex the flow (e.g., packet or timeslot) on the input link.
� Switch the flow element onto the appropriateoutput link.
Multiplex the flows on the output link.
Manjunath: Computer Communicatin Networks – p.32
Functions of a Switch
� Two categories, also called planes offunctions—data plane and control plane
� Data plane functions
� Demultiplex the flow (e.g., packet or timeslot) on the input link.
� Switch the flow element onto the appropriateoutput link.
� Multiplex the flows on the output link.
Manjunath: Computer Communicatin Networks – p.32
Functions of a Switch
� This implies every packet or slot in a TDM frameneeds to be processed.
Thus these are fast timescalefunctions—performed per packet or per frame.
Specialised hardware may be used for these highspeed functions.
Manjunath: Computer Communicatin Networks – p.33
Functions of a Switch
� This implies every packet or slot in a TDM frameneeds to be processed.
� Thus these are fast timescalefunctions—performed per packet or per frame.
Specialised hardware may be used for these highspeed functions.
Manjunath: Computer Communicatin Networks – p.33
Functions of a Switch
� This implies every packet or slot in a TDM frameneeds to be processed.
� Thus these are fast timescalefunctions—performed per packet or per frame.
� Specialised hardware may be used for these highspeed functions.
Manjunath: Computer Communicatin Networks – p.33
Functions of a SwitchControl plane functions
� Connection setup and resourceallocation/reservation
Achieved through source-network andswitch-switch signalling
Functions performed over connection (flow)arrival timescales
General purpose processors can be used;Increasing interest in parallelisation
Routing and local conditions informationdissemination and computation, usuallyperformed at timescales at which trafficcharacteristics change
Manjunath: Computer Communicatin Networks – p.34
Functions of a SwitchControl plane functions
� Connection setup and resourceallocation/reservation
� Achieved through source-network andswitch-switch signalling
Functions performed over connection (flow)arrival timescales
General purpose processors can be used;Increasing interest in parallelisation
Routing and local conditions informationdissemination and computation, usuallyperformed at timescales at which trafficcharacteristics change
Manjunath: Computer Communicatin Networks – p.34
Functions of a SwitchControl plane functions
� Connection setup and resourceallocation/reservation
� Achieved through source-network andswitch-switch signalling
� Functions performed over connection (flow)arrival timescales
General purpose processors can be used;Increasing interest in parallelisation
Routing and local conditions informationdissemination and computation, usuallyperformed at timescales at which trafficcharacteristics change
Manjunath: Computer Communicatin Networks – p.34
Functions of a SwitchControl plane functions
� Connection setup and resourceallocation/reservation
� Achieved through source-network andswitch-switch signalling
� Functions performed over connection (flow)arrival timescales
� General purpose processors can be used;Increasing interest in parallelisation
Routing and local conditions informationdissemination and computation, usuallyperformed at timescales at which trafficcharacteristics change
Manjunath: Computer Communicatin Networks – p.34
Functions of a SwitchControl plane functions
� Connection setup and resourceallocation/reservation
� Achieved through source-network andswitch-switch signalling
� Functions performed over connection (flow)arrival timescales
� General purpose processors can be used;Increasing interest in parallelisation
� Routing and local conditions informationdissemination and computation, usuallyperformed at timescales at which trafficcharacteristics change
Manjunath: Computer Communicatin Networks – p.34
Design Issues in a Packet Switch
� Input and output lines could be slotted orunslotted—correspondingly, packets lengths andinterarrival time have a discrete or continuousdistributions
Packet lengths could be fixed or variable
Datagram packet switches: Every packet of aflow is treated independent of previous packets inthe flow
Control and signalling functions includepopulating the routing table, participating indistributed algorithms associated, for example,with routing.
Manjunath: Computer Communicatin Networks – p.35
Design Issues in a Packet Switch
� Input and output lines could be slotted orunslotted—correspondingly, packets lengths andinterarrival time have a discrete or continuousdistributions
� Packet lengths could be fixed or variable
Datagram packet switches: Every packet of aflow is treated independent of previous packets inthe flow
Control and signalling functions includepopulating the routing table, participating indistributed algorithms associated, for example,with routing.
Manjunath: Computer Communicatin Networks – p.35
Design Issues in a Packet Switch
� Input and output lines could be slotted orunslotted—correspondingly, packets lengths andinterarrival time have a discrete or continuousdistributions
� Packet lengths could be fixed or variable
� Datagram packet switches: Every packet of aflow is treated independent of previous packets inthe flow
Control and signalling functions includepopulating the routing table, participating indistributed algorithms associated, for example,with routing.
Manjunath: Computer Communicatin Networks – p.35
Design Issues in a Packet Switch
� Input and output lines could be slotted orunslotted—correspondingly, packets lengths andinterarrival time have a discrete or continuousdistributions
� Packet lengths could be fixed or variable
� Datagram packet switches: Every packet of aflow is treated independent of previous packets inthe flow
� Control and signalling functions includepopulating the routing table, participating indistributed algorithms associated, for example,with routing.
Manjunath: Computer Communicatin Networks – p.35
Design Issues in a Packet Switch
� Virtual circuit packets switches
Connection setup to allocate path andresources on links on path to the flowPackets are assigned link level labels andswitched based on labelsPerformance measures: Switching delay ingetting to the output queue, packet loss rate,
Manjunath: Computer Communicatin Networks – p.36
Design Issues in a Packet Switch
� Virtual circuit packets switches
� Connection setup to allocate path andresources on links on path to the flow
Packets are assigned link level labels andswitched based on labelsPerformance measures: Switching delay ingetting to the output queue, packet loss rate,
Manjunath: Computer Communicatin Networks – p.36
Design Issues in a Packet Switch
� Virtual circuit packets switches
� Connection setup to allocate path andresources on links on path to the flow
� Packets are assigned link level labels andswitched based on labels
Performance measures: Switching delay ingetting to the output queue, packet loss rate,
Manjunath: Computer Communicatin Networks – p.36
Design Issues in a Packet Switch
� Virtual circuit packets switches
� Connection setup to allocate path andresources on links on path to the flow
� Packets are assigned link level labels andswitched based on labels
� Performance measures: Switching delay ingetting to the output queue, packet loss rate,
Manjunath: Computer Communicatin Networks – p.36
Components of a Packet Switch
processing
O/p Queue Scheduling,
processing
O/p Queue Scheduling,
Control and Signalling Functions
Switch
Fabric
Interface
Line
Input Processing& Forwarding
Queuing &Scheduling
Queuing &Scheduling
LineInterface
Line
Input Processing& Forwarding
Interface
InterfaceLine
Manjunath: Computer Communicatin Networks – p.37
Call Setup in a Circuit Switch
� Detect off hook, apply dial tone, accept digits,perform digit analysis
From routing algorithm determine next switch onpath to destination and perform signalling toreserve channel on link to the switch
If path is available reserve resources and“program” the pair “output port:TDM slot” forthe channel on the incoming port of the call
Maintain call
Release resources on completing the call andperform possible billing functions
Manjunath: Computer Communicatin Networks – p.38
Call Setup in a Circuit Switch
� Detect off hook, apply dial tone, accept digits,perform digit analysis
� From routing algorithm determine next switch onpath to destination and perform signalling toreserve channel on link to the switch
If path is available reserve resources and“program” the pair “output port:TDM slot” forthe channel on the incoming port of the call
Maintain call
Release resources on completing the call andperform possible billing functions
Manjunath: Computer Communicatin Networks – p.38
Call Setup in a Circuit Switch
� Detect off hook, apply dial tone, accept digits,perform digit analysis
� From routing algorithm determine next switch onpath to destination and perform signalling toreserve channel on link to the switch
� If path is available reserve resources and“program” the pair “output port:TDM slot” forthe channel on the incoming port of the call
Maintain call
Release resources on completing the call andperform possible billing functions
Manjunath: Computer Communicatin Networks – p.38
Call Setup in a Circuit Switch
� Detect off hook, apply dial tone, accept digits,perform digit analysis
� From routing algorithm determine next switch onpath to destination and perform signalling toreserve channel on link to the switch
� If path is available reserve resources and“program” the pair “output port:TDM slot” forthe channel on the incoming port of the call
� Maintain call
Release resources on completing the call andperform possible billing functions
Manjunath: Computer Communicatin Networks – p.38
Call Setup in a Circuit Switch
� Detect off hook, apply dial tone, accept digits,perform digit analysis
� From routing algorithm determine next switch onpath to destination and perform signalling toreserve channel on link to the switch
� If path is available reserve resources and“program” the pair “output port:TDM slot” forthe channel on the incoming port of the call
� Maintain call
� Release resources on completing the call andperform possible billing functions
Manjunath: Computer Communicatin Networks – p.38
Call Setup in a Circuit Switch
Call Teardown Delay
Call Processing Delay
Dial Tone Delay
Information Transfer
Calling Phone Switch
Call Complete Signal (On Hook)
Dial digits
Apply dial tone
Phone goes off hook
time
Call Accept (or Deny) Signal
Manjunath: Computer Communicatin Networks – p.39
Functions of a Circuit Switch
� Switching function like setting up circuit insideswitch between input and output and maintain itfor duration of call
Call processing functions like off-hook detection,digit acceptance and analysis, routing call andcorresponding signaling for path reservation andbilling functions
Background functions for executing the routingprotocols and algorithms, management andmaintenance of the switch.
Manjunath: Computer Communicatin Networks – p.40
Functions of a Circuit Switch
� Switching function like setting up circuit insideswitch between input and output and maintain itfor duration of call
� Call processing functions like off-hook detection,digit acceptance and analysis, routing call andcorresponding signaling for path reservation andbilling functions
Background functions for executing the routingprotocols and algorithms, management andmaintenance of the switch.
Manjunath: Computer Communicatin Networks – p.40
Functions of a Circuit Switch
� Switching function like setting up circuit insideswitch between input and output and maintain itfor duration of call
� Call processing functions like off-hook detection,digit acceptance and analysis, routing call andcorresponding signaling for path reservation andbilling functions
� Background functions for executing the routingprotocols and algorithms, management andmaintenance of the switch.
Manjunath: Computer Communicatin Networks – p.40
Circuit Switch: Logical View
Switc
h Fab
ricInput i x
TDM Frame TDM Frame
Control Processor
Output oy
Manjunath: Computer Communicatin Networks – p.41
Operation of a Circuit Switch
� Each slot on each input line contains theinformation flow unit for a circuit.
At the time of circuit set up, the switchingpattern—output port and the slot in the outputport, is determined.
The fabric will perform the switching operationwhich is repeated in every frame.
In figure, the contents of slot on input line areswitched to slot on line .
Manjunath: Computer Communicatin Networks – p.42
Operation of a Circuit Switch
� Each slot on each input line contains theinformation flow unit for a circuit.
� At the time of circuit set up, the switchingpattern—output port and the slot in the outputport, is determined.
The fabric will perform the switching operationwhich is repeated in every frame.
In figure, the contents of slot on input line areswitched to slot on line .
Manjunath: Computer Communicatin Networks – p.42
Operation of a Circuit Switch
� Each slot on each input line contains theinformation flow unit for a circuit.
� At the time of circuit set up, the switchingpattern—output port and the slot in the outputport, is determined.
� The fabric will perform the switching operationwhich is repeated in every frame.
In figure, the contents of slot on input line areswitched to slot on line .
Manjunath: Computer Communicatin Networks – p.42
Operation of a Circuit Switch
� Each slot on each input line contains theinformation flow unit for a circuit.
� At the time of circuit set up, the switchingpattern—output port and the slot in the outputport, is determined.
� The fabric will perform the switching operationwhich is repeated in every frame.
� In figure, the contents of slot ��� on input line
�
areswitched to slot ��� on line �.
Manjunath: Computer Communicatin Networks – p.42
Routing
� A route is an ordered sequence of links between asource and a destination.
A network node, or a switch, performs therouting function along with multiplexing andswitching. However, routing is a “network wide”function and the nodes collaborate in makingrouting decisions.
Often, routing and forwarding are usedsynonymously and this is wrong!
An incoming packet is processed, its output portdetermined and then the packet is forwarded tothe output link. Thus forwarding is a fasttimescale operation and is a data plane function,meaning it operates on the data.
Manjunath: Computer Communicatin Networks – p.43
Routing
� A route is an ordered sequence of links between asource and a destination.
� A network node, or a switch, performs therouting function along with multiplexing andswitching. However, routing is a “network wide”function and the nodes collaborate in makingrouting decisions.
Often, routing and forwarding are usedsynonymously and this is wrong!
An incoming packet is processed, its output portdetermined and then the packet is forwarded tothe output link. Thus forwarding is a fasttimescale operation and is a data plane function,meaning it operates on the data.
Manjunath: Computer Communicatin Networks – p.43
Routing
� A route is an ordered sequence of links between asource and a destination.
� A network node, or a switch, performs therouting function along with multiplexing andswitching. However, routing is a “network wide”function and the nodes collaborate in makingrouting decisions.
� Often, routing and forwarding are usedsynonymously and this is wrong!
An incoming packet is processed, its output portdetermined and then the packet is forwarded tothe output link. Thus forwarding is a fasttimescale operation and is a data plane function,meaning it operates on the data.
Manjunath: Computer Communicatin Networks – p.43
Routing
� A route is an ordered sequence of links between asource and a destination.
� A network node, or a switch, performs therouting function along with multiplexing andswitching. However, routing is a “network wide”function and the nodes collaborate in makingrouting decisions.
� Often, routing and forwarding are usedsynonymously and this is wrong!
� An incoming packet is processed, its output portdetermined and then the packet is forwarded tothe output link. Thus forwarding is a fasttimescale operation and is a data plane function,meaning it operates on the data.
Manjunath: Computer Communicatin Networks – p.43
Routing
� The decision of which output port this packetshould be sent is made on slower timescale. Thisdepends on the route that the packet will take inthe network. Thus this is a control plane activity.
The forwarding function consults a routing tableto decide the output port for a packet. The routingfunction nopulates this routing table.
Manjunath: Computer Communicatin Networks – p.44
Routing
� The decision of which output port this packetshould be sent is made on slower timescale. Thisdepends on the route that the packet will take inthe network. Thus this is a control plane activity.
� The forwarding function consults a routing tableto decide the output port for a packet. The routingfunction nopulates this routing table.
Manjunath: Computer Communicatin Networks – p.44
Routing: Computation Models
� Objective of routing algorithm: Use networkresources efficiently—conflicts of providing QoSto a customers and utilise network resourcesefficiently needs to be addressed.
Network topology information and userrequirements need to be known.
Routing decisions can be centralised ordistributed.
Manjunath: Computer Communicatin Networks – p.45
Routing: Computation Models
� Objective of routing algorithm: Use networkresources efficiently—conflicts of providing QoSto a customers and utilise network resourcesefficiently needs to be addressed.
� Network topology information and userrequirements need to be known.
Routing decisions can be centralised ordistributed.
Manjunath: Computer Communicatin Networks – p.45
Routing: Computation Models
� Objective of routing algorithm: Use networkresources efficiently—conflicts of providing QoSto a customers and utilise network resourcesefficiently needs to be addressed.
� Network topology information and userrequirements need to be known.
� Routing decisions can be centralised ordistributed.
Manjunath: Computer Communicatin Networks – p.45
Routing: Computation Models
� In centralised routing the network topologyinformation is collected using a distributedalgorithm at a central node where the routes aredetermined for every possible source-destinationpair. These routing decisions communicated to allthe nodes in the network.
In distributed routing, distributed algorithms areused to collect topology information and makerouting decisions.
Information aggregation may be used to minimise“information explosion”. An obvious solution isuse of hierarchies.
Manjunath: Computer Communicatin Networks – p.46
Routing: Computation Models
� In centralised routing the network topologyinformation is collected using a distributedalgorithm at a central node where the routes aredetermined for every possible source-destinationpair. These routing decisions communicated to allthe nodes in the network.
� In distributed routing, distributed algorithms areused to collect topology information and makerouting decisions.
Information aggregation may be used to minimise“information explosion”. An obvious solution isuse of hierarchies.
Manjunath: Computer Communicatin Networks – p.46
Routing: Computation Models
� In centralised routing the network topologyinformation is collected using a distributedalgorithm at a central node where the routes aredetermined for every possible source-destinationpair. These routing decisions communicated to allthe nodes in the network.
� In distributed routing, distributed algorithms areused to collect topology information and makerouting decisions.
� Information aggregation may be used to minimise“information explosion”. An obvious solution isuse of hierarchies.
Manjunath: Computer Communicatin Networks – p.46
Distributed RoutingDecision Models
� Source Routing: The decision on the sequence ofthe links to the destination may be made at thesource.
The routing information is embedded into thepacket and is used by the intermediate nodes inthe network to forward the packet appropriately.
Hop-by-Hop Routing: Each node only knows the‘next node on the best route’ to the destination.The nodes need not know the entire route to thedestinations.
Manjunath: Computer Communicatin Networks – p.47
Distributed RoutingDecision Models
� Source Routing: The decision on the sequence ofthe links to the destination may be made at thesource.
� The routing information is embedded into thepacket and is used by the intermediate nodes inthe network to forward the packet appropriately.
Hop-by-Hop Routing: Each node only knows the‘next node on the best route’ to the destination.The nodes need not know the entire route to thedestinations.
Manjunath: Computer Communicatin Networks – p.47
Distributed RoutingDecision Models
� Source Routing: The decision on the sequence ofthe links to the destination may be made at thesource.
� The routing information is embedded into thepacket and is used by the intermediate nodes inthe network to forward the packet appropriately.
� Hop-by-Hop Routing: Each node only knows the‘next node on the best route’ to the destination.The nodes need not know the entire route to thedestinations.
Manjunath: Computer Communicatin Networks – p.47
Tasks in Routing
� Exchange of local topology information withneighbours at faster timescales.
This helps keep track of link status and and alsothe demands on the links. The latter helps indetermining QoS capabilities of the routes.
Perform any aggregation that may be required bythe algorithms and disseminate aggregatedinformation.
A Routing Protocol will be used to exchangeinformation that is necessary for the routingalgorithm
Manjunath: Computer Communicatin Networks – p.48
Tasks in Routing
� Exchange of local topology information withneighbours at faster timescales.
� This helps keep track of link status and and alsothe demands on the links. The latter helps indetermining QoS capabilities of the routes.
Perform any aggregation that may be required bythe algorithms and disseminate aggregatedinformation.
A Routing Protocol will be used to exchangeinformation that is necessary for the routingalgorithm
Manjunath: Computer Communicatin Networks – p.48
Tasks in Routing
� Exchange of local topology information withneighbours at faster timescales.
� This helps keep track of link status and and alsothe demands on the links. The latter helps indetermining QoS capabilities of the routes.
� Perform any aggregation that may be required bythe algorithms and disseminate aggregatedinformation.
A Routing Protocol will be used to exchangeinformation that is necessary for the routingalgorithm
Manjunath: Computer Communicatin Networks – p.48
Tasks in Routing
� Exchange of local topology information withneighbours at faster timescales.
� This helps keep track of link status and and alsothe demands on the links. The latter helps indetermining QoS capabilities of the routes.
� Perform any aggregation that may be required bythe algorithms and disseminate aggregatedinformation.
� A Routing Protocol will be used to exchangeinformation that is necessary for the routingalgorithm
Manjunath: Computer Communicatin Networks – p.48
Tasks in Routing
� Route computations are based on the topologyinformation collected and use a routingalgorithm.
Topology information exchange always occurs.Route computation may be triggered and/or timedriven.
Granularity of route computationFine grained on demand routing on a persession basis.Coarse grained per flow routing where fatpipes are a priori set up.
Manjunath: Computer Communicatin Networks – p.49
Tasks in Routing
� Route computations are based on the topologyinformation collected and use a routingalgorithm.
� Topology information exchange always occurs.Route computation may be triggered and/or timedriven.
Granularity of route computationFine grained on demand routing on a persession basis.Coarse grained per flow routing where fatpipes are a priori set up.
Manjunath: Computer Communicatin Networks – p.49
Tasks in Routing
� Route computations are based on the topologyinformation collected and use a routingalgorithm.
� Topology information exchange always occurs.Route computation may be triggered and/or timedriven.
� Granularity of route computation
Fine grained on demand routing on a persession basis.Coarse grained per flow routing where fatpipes are a priori set up.
Manjunath: Computer Communicatin Networks – p.49
Tasks in Routing
� Route computations are based on the topologyinformation collected and use a routingalgorithm.
� Topology information exchange always occurs.Route computation may be triggered and/or timedriven.
� Granularity of route computation
� Fine grained on demand routing on a persession basis.
Coarse grained per flow routing where fatpipes are a priori set up.
Manjunath: Computer Communicatin Networks – p.49
Tasks in Routing
� Route computations are based on the topologyinformation collected and use a routingalgorithm.
� Topology information exchange always occurs.Route computation may be triggered and/or timedriven.
� Granularity of route computation
� Fine grained on demand routing on a persession basis.
� Coarse grained per flow routing where fatpipes are a priori set up.
Manjunath: Computer Communicatin Networks – p.49
Design and Performance Issues
� Routing protocols: What information toexchange, how often, how to exchange
Routing Algorithms: Objective functions for besteffort routing and QoS routing
Multicast routing algorithms
Routing protocols and algorithms for rapidlychanging topologies, e.g., ad hoc networks
Manjunath: Computer Communicatin Networks – p.50
Design and Performance Issues
� Routing protocols: What information toexchange, how often, how to exchange
� Routing Algorithms: Objective functions for besteffort routing and QoS routing
Multicast routing algorithms
Routing protocols and algorithms for rapidlychanging topologies, e.g., ad hoc networks
Manjunath: Computer Communicatin Networks – p.50
Design and Performance Issues
� Routing protocols: What information toexchange, how often, how to exchange
� Routing Algorithms: Objective functions for besteffort routing and QoS routing
� Multicast routing algorithms
Routing protocols and algorithms for rapidlychanging topologies, e.g., ad hoc networks
Manjunath: Computer Communicatin Networks – p.50
Design and Performance Issues
� Routing protocols: What information toexchange, how often, how to exchange
� Routing Algorithms: Objective functions for besteffort routing and QoS routing
� Multicast routing algorithms
� Routing protocols and algorithms for rapidlychanging topologies, e.g., ad hoc networks
Manjunath: Computer Communicatin Networks – p.50
Design and Performance Issues
� Performance measures: Connection blockingprobability, load imposed on the network,adaptation to changes in the network conditions.
Connection blocking only relevant in connectionbased networks. Typically associated with circuitmultiplexed networks.
In datagram networks, connections are not set up.Hence no concept of connection blocking.
Virtual circuit based networks use packetmultiplexing but set up a connection before datatransfer begins to alert the switches of thecreation of a flow.
Manjunath: Computer Communicatin Networks – p.51
Design and Performance Issues
� Performance measures: Connection blockingprobability, load imposed on the network,adaptation to changes in the network conditions.
� Connection blocking only relevant in connectionbased networks. Typically associated with circuitmultiplexed networks.
In datagram networks, connections are not set up.Hence no concept of connection blocking.
Virtual circuit based networks use packetmultiplexing but set up a connection before datatransfer begins to alert the switches of thecreation of a flow.
Manjunath: Computer Communicatin Networks – p.51
Design and Performance Issues
� Performance measures: Connection blockingprobability, load imposed on the network,adaptation to changes in the network conditions.
� Connection blocking only relevant in connectionbased networks. Typically associated with circuitmultiplexed networks.
� In datagram networks, connections are not set up.Hence no concept of connection blocking.
Virtual circuit based networks use packetmultiplexing but set up a connection before datatransfer begins to alert the switches of thecreation of a flow.
Manjunath: Computer Communicatin Networks – p.51
Design and Performance Issues
� Performance measures: Connection blockingprobability, load imposed on the network,adaptation to changes in the network conditions.
� Connection blocking only relevant in connectionbased networks. Typically associated with circuitmultiplexed networks.
� In datagram networks, connections are not set up.Hence no concept of connection blocking.
� Virtual circuit based networks use packetmultiplexing but set up a connection before datatransfer begins to alert the switches of thecreation of a flow.
Manjunath: Computer Communicatin Networks – p.51
Network Management
� Handle conditions for which the network is notengineered. Different from ‘congestion control’where the overload conditions are short lived.
All operational networks define a managementarchitecture to collect and control the networkresources.
Performance data are collected by managednetwork devices these are in turn are gathered bya network management station in the network thatwill analyse the data that has been collected.
Manjunath: Computer Communicatin Networks – p.52
Network Management
� Handle conditions for which the network is notengineered. Different from ‘congestion control’where the overload conditions are short lived.
� All operational networks define a managementarchitecture to collect and control the networkresources.
Performance data are collected by managednetwork devices these are in turn are gathered bya network management station in the network thatwill analyse the data that has been collected.
Manjunath: Computer Communicatin Networks – p.52
Network Management
� Handle conditions for which the network is notengineered. Different from ‘congestion control’where the overload conditions are short lived.
� All operational networks define a managementarchitecture to collect and control the networkresources.
� Performance data are collected by managednetwork devices these are in turn are gathered bya network management station in the network thatwill analyse the data that has been collected.
Manjunath: Computer Communicatin Networks – p.52
Network Management
� The management architecture provides somecontrol functions that can be performed on remotemanaged devices by management stations eitherin a programmed manner or through an operator
Security issues are also handled by a networkmanagement architecture.
Manjunath: Computer Communicatin Networks – p.53
Network Management
� The management architecture provides somecontrol functions that can be performed on remotemanaged devices by management stations eitherin a programmed manner or through an operator
� Security issues are also handled by a networkmanagement architecture.
Manjunath: Computer Communicatin Networks – p.53
Network Management
� The management architecture provides somecontrol functions that can be performed on remotemanaged devices by management stations eitherin a programmed manner or through an operator
� Security issues are also handled by a networkmanagement architecture.
Manjunath: Computer Communicatin Networks – p.53
Traffic Controls and Timescales
� Network functions cover a wide variety oftimescales—of the order of a few microsecondsto minutes to months and years.Rather thanconsider absolute time we identify the followingfour relative timescales.
1. Packet timescale (packet transmission time;seconds or milliseconds)
2. Session, call or flow timescale (typicallyminutes)
3. Busy hour or traffic variation timescale(typically hours)
4. Provisioning timescale (usually hours to daysor weeks)
Manjunath: Computer Communicatin Networks – p.54
Traffic Controls and Timescales
� Network functions cover a wide variety oftimescales—of the order of a few microsecondsto minutes to months and years.Rather thanconsider absolute time we identify the followingfour relative timescales.1. Packet timescale (packet transmission time;
�seconds or milliseconds)
2. Session, call or flow timescale (typicallyminutes)
3. Busy hour or traffic variation timescale(typically hours)
4. Provisioning timescale (usually hours to daysor weeks)
Manjunath: Computer Communicatin Networks – p.54
Traffic Controls and Timescales
� Network functions cover a wide variety oftimescales—of the order of a few microsecondsto minutes to months and years.Rather thanconsider absolute time we identify the followingfour relative timescales.1. Packet timescale (packet transmission time;
�seconds or milliseconds)2. Session, call or flow timescale (typically
minutes)
3. Busy hour or traffic variation timescale(typically hours)
4. Provisioning timescale (usually hours to daysor weeks)
Manjunath: Computer Communicatin Networks – p.54
Traffic Controls and Timescales
� Network functions cover a wide variety oftimescales—of the order of a few microsecondsto minutes to months and years.Rather thanconsider absolute time we identify the followingfour relative timescales.1. Packet timescale (packet transmission time;
�seconds or milliseconds)2. Session, call or flow timescale (typically
minutes)3. Busy hour or traffic variation timescale
(typically hours)
4. Provisioning timescale (usually hours to daysor weeks)
Manjunath: Computer Communicatin Networks – p.54
Traffic Controls and Timescales
� Network functions cover a wide variety oftimescales—of the order of a few microsecondsto minutes to months and years.Rather thanconsider absolute time we identify the followingfour relative timescales.1. Packet timescale (packet transmission time;
�seconds or milliseconds)2. Session, call or flow timescale (typically
minutes)3. Busy hour or traffic variation timescale
(typically hours)4. Provisioning timescale (usually hours to days
or weeks)
Manjunath: Computer Communicatin Networks – p.54
Traffic Controls and Timescales
� Packet timescale controls discriminate betweentreatment of individual packets (e.g.,transmissionscheduling, buffer allocation).
Accepting and the routing of a call in connectionoriented networks are made on slower timescales,those of the order of session interarrival times.
Since traffic processes vary over a day/week andprobably have some cyclical patterns, resourceallocation algorithms and thresholds may need tochanged at the rate at which traffic processes inthe network change.
Resource provisioning occurs over longerperiods, of say months, to years.
Manjunath: Computer Communicatin Networks – p.55
Traffic Controls and Timescales
� Packet timescale controls discriminate betweentreatment of individual packets (e.g.,transmissionscheduling, buffer allocation).
� Accepting and the routing of a call in connectionoriented networks are made on slower timescales,those of the order of session interarrival times.
Since traffic processes vary over a day/week andprobably have some cyclical patterns, resourceallocation algorithms and thresholds may need tochanged at the rate at which traffic processes inthe network change.
Resource provisioning occurs over longerperiods, of say months, to years.
Manjunath: Computer Communicatin Networks – p.55
Traffic Controls and Timescales
� Packet timescale controls discriminate betweentreatment of individual packets (e.g.,transmissionscheduling, buffer allocation).
� Accepting and the routing of a call in connectionoriented networks are made on slower timescales,those of the order of session interarrival times.
� Since traffic processes vary over a day/week andprobably have some cyclical patterns, resourceallocation algorithms and thresholds may need tochanged at the rate at which traffic processes inthe network change.
Resource provisioning occurs over longerperiods, of say months, to years.
Manjunath: Computer Communicatin Networks – p.55
Traffic Controls and Timescales
� Packet timescale controls discriminate betweentreatment of individual packets (e.g.,transmissionscheduling, buffer allocation).
� Accepting and the routing of a call in connectionoriented networks are made on slower timescales,those of the order of session interarrival times.
� Since traffic processes vary over a day/week andprobably have some cyclical patterns, resourceallocation algorithms and thresholds may need tochanged at the rate at which traffic processes inthe network change.
� Resource provisioning occurs over longerperiods, of say months, to years.
Manjunath: Computer Communicatin Networks – p.55